FIGS. 5 and 6 are respectively axial sectional views of conventional fastening apparatuses 50 and 60 for securing a wheel or the like to a shaft. In such a fastening apparatus as described, shoulders 54 and 64 are provided in boss holes 53 and 63 of wheels 52 and 62, respectively, to prevent relative movement between outer rings 51 and 61 and wheels 52 and 62. Wheels 52 and 62 need be provided with relatively long guide or hub portions 56 and 66 in contact with shafts 55 and 65 to prevent an error in angle between the shafts 55 and 65 and the wheels 52 and 62, that is, to provide centering therebetween. However, it is troublesome to machine the shoulders 54 and 64 and the guide portions 56 and 66 on the wheels. Moreover, in mounting the fastening apparatus, attention should be paid to directivity of the wheels 52 and 62.
The aforementioned problem is solved by the present invention which provides an improved apparatus for fastening a wheel or wheel-like body, having a boss hole therein, to a shaft. The fastening apparatus includes an axially slit outer ring having a cylindrical outer peripheral surface fitted into the boss hole, a tapered inner peripheral surface, a support flange formed at one end of the ring adjacent the small diameter end of the tapered inner peripheral surface for direct engagement with the shaft, a cylindrical inner peripheral surface formed at the large diameter end of the tapered inner peripheral surface, and an enlarged annular end flange formed at the other end of the ring. The fastening apparatus also includes an inner ring having a cylindrical inner peripheral surface for direct engagement with the shaft, a tapered outer peripheral surface complementary to the tapered inner peripheral surface of the outer ring, a cylindrical outer peripheral surface formed at the large diameter end of the tapered outer peripheral surface and complementary to the cylindrical inner peripheral surface of the outer ring, a flange portion enlarged in diameter formed at the large diameter end of the tapered outer peripheral surface, nonthreaded axial holes formed through the flange portion, and an axial slit. Bolts threadedly engage with tapped holes formed in the wheel or wheel-like body while extending through the nonthreaded holes.
When bolts are fastened, the outer and inner rings are relatively axially moved. However, since the end flange of the outer ring is in contact with an end face of the wheel, the wheel and the outer ring are prevented from relative axial movement. When the bolts are further fastened, the outer ring and the inner ring are fastened to the wheel and the shaft, respectively, by the wedge action of the tapered surfaces of the outer and inner rings and the respective resilient radial expansion and contraction of the outer and inner rings. As the result, the shaft and the wheel are firmly fastened, and torque can be transmitted therebetween by frictional force.
In the fastening operation, on the side of the small diameter of the tapered surfaces, the support flange on the outer ring comes into contact with the outer peripheral surface of the shaft, and the shaft and wheel are subjected to centering. On the side of the large diameter of the tapered surfaces, the shaft and the wheel are subjected to centering by the provision of the cylindrical outer peripheral surface of the outer ring, the cylindrical inner peripheral surface of the outer ring and the cylindrical outer peripheral surface of the inner ring which are complementary to one another, and the cylindrical inner peripheral surface of the inner ring. In the present invention, the boss hole of the wheel can be a circular hole of uniform diameter without requiring shoulders and/or guide portions as in prior art devices. Accordingly, machining is easy, and in mounting, attention need not be paid to the directivity of the wheel.